I don't know anything about ACCA so nothing from me on that side.
BBA has a few kinds - IT, Marketing, HRM and Finance. At least these are all I can remember.
IT, again for good brains.
Finance is for calculations. A very dry field and often complicated.
Marketing is good if you have innovative brains. You need to have ideas on how to promote the company.
HRM - hiring, firing, training, forecasting how much staff you need, etc.
I have summed up the above the best I could. Since HR is a relatively newer field, most opt for this and I personally think it's not hard even. Many small companies now have an HR department too. However, like Vicky said, the initial stages are the same for all so you can decide later.
BBAs are for average students like myself. If you have good brains and patience to tackle difficult stuff, choose BSc. It is more rewarding right after graduation without Masters' even although I would insist you do complete Masters' as well.
If you can remember my words till four years later, please forget about MBA. It is as common as BA was in our fathers' times. MS is the latest degree now.
You asked about uni........according to myself, AIR, Bahria, SZABIST are all the same. SZABIST's name came for a few years in Asiaweek or Newsweek but that is past. The only thing that once happened at Bahria is that they forced everyone to purchase outdated laptops at fifteen thousand more than market rate whereas AIR University gave it three thousand cheaper and optional. Fee structure, a student can guide.
MAJU, I would rank just as common as Lahore University or COMSATS so keep it your second priority.
I myself am from Preston. Many look down upon if for reasons God knows best. It was Preston that was the first private uni in the entire country and that gave an ideology to others. There are more merits to it but i'd rather not get into that. One of the good things about it is that fee has to be paid monthly and is pretty much cheaper. Whenever I used to insist to pay for the entire semester, the admin would get a problem.
Once in university, you must remember that this is a stage where you are let out on almost entirely our own. Thus, you need to behave sensibly since you actually get more responsibility. The friends you choose must be the right ones. Four years together at grown up ages makes you stick to them throughout your life. Results of all subjects are calculted in terms of GPA and this is carried forward to the next semester and the next and so on till you finally graduate so be equally serious about all tests, attendance and assignments. A low GPA can even kick you out of the uni. M saying this particularly because you might be coming here, away from parents and at the moment I see you are still not mature enough to be let on your own.
In advance, welcome to Islamabad, uni life and best of luck!